The present invention relates to a hydraulic brake system.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
It is desired that the axle on which the electric machine is located, maximally recoups energy during a braking process. This means that a mechanical, in particular hydraulic, brake system which is connected in parallel to the electric machine is to brake as little as possible in this operating condition to convert an as great as possible portion of the braking energy into electric energy. However, for a variety of reasons the recouping capacity of the system which consists of the electric machine and the connected energy accumulator is variable. The recouping capacity depends for example on the charge state of the battery or the temperature of the electric machine. The brake system therefore has to be “blending-enabled”, i.e. the brake power has to be capable of being distributed between the hydraulic brake system and the brake power generated by recouping.
From DE 10 2009 048 785 A1 a motor vehicle with a hydraulic drive is known which has an electric machine for recouping energy. The hydraulic brake system has a pressure-reduction valve device to lower the pressure generated by the hydraulic brake system in the recouping phase.
It is also known to use a brake power assist unit and as the case may be a hydro-aggregate, i.e, a block with valves and a pump, in order to obtain a blending-enabled brake system. However, it is difficult to configure these components so that a blending process is not perceived by the driver. Achieving this requires that the pedal force and the pedal travel perform like in a conventional braking process during a recouping.
It would therefore be desirable and advantageous to provide a blending-enabled brake system, wherein a changed distribution of the brake power is not to be perceived by the driver